1. Field of the Invention
The present invention relates to a taking lens apparatus, and more particularly, to a taking lens apparatus comprising an optical system for focusing state determination and an image-capturing element.
2. Description of the Related Art
Japanese Patent Application Publication No. 55-76312 and Japanese Patent Publication No. 7-60211 disclose conventional methods for determining a focusing state (front-focusing, rear-focusing or just-focusing state) of a taking lens apparatus using a plurality of image-capturing elements with different optical path lengths from the taking lens. For example, for an image-capturing element for capturing video images (video image-capturing element), two focusing state determination image-capturing elements for capturing images in the same picture-taking range are placed in a position to which optical path length is longer and a position to which optical path length is shorter than that of the video image-capturing element, respectively. Then, focus estimation values for the respective image-capturing faces of the respective focusing state determination image-capturing elements are calculated and compared according to high frequency components of the video signals obtained from these focusing state determination image-capturing elements. Thus, the focusing state of the image-capturing face of the video image-capturing element is determined, that is, whether it is front-focusing, rear-focusing or just-focusing state according to a comparison between the focus estimation values. Such a focusing state determination method is applicable to focus determination for auto focusing, etc.
The object light for focusing state determination can be obtained by splitting video object light that passes through the taking lens. In this case, in addition to a usual picture-taking optical system, a focusing state determination optical system is constructed for the taking lens. Therefore, optical (mechanical) adjustments are required not only for the usual picture-taking optical system but also for the focusing state determination optical system at the time of factory shipment. Furthermore, when using the taking lens apparatus, the user may have to adjust the focusing state determination optical system due to manufacturing errors, etc. of the camera body.
The present invention has been implemented in view of the circumstances described above and it is an object of the present invention to provide a taking lens apparatus capable of easily adjusting the focusing state determination optical system and performing accurate focusing state determination.
To attain the above-described object, the present invention is directed to a taking lens apparatus to be mounted on a camera body, the taking lens apparatus comprising: a taking lens; a light splitting device which splits object light passing through the taking lens into focusing state determination object light and video object light entering a video image-capturing element of the camera body; focusing state determination image-capturing elements which capture images of the focusing state determination object light split by the light splitting device; a supporting device which movably supports the focusing state determination image-capturing elements so that optical path lengths for the focusing state determination object light entering the focusing state determination image-capturing elements are variable; and an adjusting device which adjusts positions of the focusing state determination image-capturing elements supported by the supporting device.
The present invention is also directed to a taking lens apparatus to be mounted on a camera body, the taking lens apparatus comprising: a taking lens; a light splitting device which splits object light passing through the taking lens into focusing state determination object light and video object light entering a video image-capturing element of the camera body; focusing state determination image-capturing elements which capture images of the focusing state determination object light split by the light splitting device; a relay lens placed on an optical path between the light splitting device and the focusing state determination image-capturing elements; a supporting device which supports the relay lens movably along an optical axis; and an adjusting device which adjusts a position of the relay lens supported by the supporting device.
Preferably, the taking lens apparatus further comprises: a main lens barrel which guides the video object light to the video image-capturing element; and a focusing state determination lens barrel which is branched from the main lens barrel and guides the focusing state determination object light to the focusing state determination image-capturing elements, the focusing state determination image-capturing elements being mounted on the focusing state determination lens barrel, wherein the adjusting device comprises an operation ring which is arranged on the focusing state determination lens barrel and adjusts the position of the focusing state determination image-capturing elements or the relay lens.
According to the present invention, there is provided the adjusting device for adjusting the focusing state determination optical system on the focusing state determination lens barrel branched from the main lens barrel, and the operator can easily adjust the focusing state determination optical system and perform accurate focusing state determination.